1. Field of the Invention
This invention relates to a pneumatically operated actuator and to a method of making the same.
2. Prior Art Statement
It is known to make a pneumatically operated actuator having a pneumatically operated movable wall interconnected by a feedback tension spring to a pilot valve positioner that is adapted to pneumatically operate the movable wall of the actuator in relation to a pneumatic signal directed to the positioner.
For example, see the following item:
(1) Piston Actuator with positioner, Model No. M50411, manufactored by the Fulton Sylphon Division of Robertshaw Controls Company and depicted in the U.S. patent to Warstler, No. 3,172,336.
It appears that the end of the feedback tension spring that is secured to the movable wall of the actuator of item (1) above is adjustably secured to the wall so that calibration of the actuator can take place through a changing of the threaded relation of a part on the one end of the spring and an adjusting means carried by the movable wall.